In a message dated 11/27/03 3:27:40 PM Eastern Standard Time,
nq5t@comcast.net writes:
> So far I am wondering about background noise level without
antenna
My opine on that subject is that it is NOT indicative in any way of
receiver noise. Rather, it's an artifact of the AGC loop in DSP and
the behavior of the system trying to find "something" in "nothing"
when AGC threshold is set to a low value and there is zip in the way
of input signal.
I don't know about you, but I generally don't run my Orion without an
antenna. It isn't quite THAT good :-)
Yep, like when you rip all four legs off the frog and say "frog jump," frog
doesn't. The conclusion is "the frog goes deaf" :-)
So DSP makes the noise? If you hear (excessive) noise in the receiver with
its antenna disconnected or shorted, it is internally generated noise by the RX
stages. It would mask very weak signals and this would explain the K6SE "weak
signal test" poor results. Blaming DSP is lame excuse. Using DSP and AN to
suppress it is a Band-Aid "fix." I will look inside the circuit (if I can
follow
schematics) and do the K6SE test to see what is going on.
I don't run my radios without antennas, but for weak signal work the internal
noise is significant and to test it you either disconnect the antenna or
short out the antenna input. That is elementary my dear Watson :-)
Yuri, K3BU
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